This invention relates to heat conversion apparatus which converts electrical energy into thermal energy and generates heat at high temperature, an ignition apparatus for igniting an exothermic system to generate heat from thereof and having a mechanism for avoiding unintended ignition, and a container with a heating function and including said ignition apparatus.
Heated containers have been in use for some years, which utilize heat generated by the self-combustion of an exothermic agent comprising an oxygen feeder and a combustible material. For instance, there are containers shown in Japanese Utility Model Provisional Publication Nos. 62-146427 and 63-42089. In these heated containers, the exothermic agent is ignited by such means as a safety fuse or a filament type electric heater connected to the exothermic agent.
The foregoing heated containers, however, are very inconvenient to use because an igniter, such as match, lighter, or a battery for operating the filament type electric heater, is separately needed. In particular, when the exothermic agent is arranged to be ignited by means of a safety fuse, there are problems such as the difficulty of use of the heated container outdoors, in rainy weather or in strong wind.
To solve the above-mentioned problems of the prior art and to improve the ignition performance, heat efficiency and heating speed, the present inventors have already proposed a variety of heated containers in which the exothermic system comprises an exothermic agent, an ignition agent arranged close to the exothermic agent and more easy to ignite than the exothermic agent, and an ignition part arranged close to the ignition agent.
For instance, in the Japanese Patent Provisional Publication No. 4-31270 of the present inventors, there is proposed a container with a heating function, which is provided with a piezoelectric element for receiving a pressure from a device having a striking force, to generate electricity, a hammer member for striking the piezoelectric element, a sensing device for sensing whether the container is filled with water or fluid of which the main component is water, ignition discharge electrodes for discharging electricity, and escaping discharge electrodes.
The foregoing container with a heating function, however, involved a risk of heat generation due to improper operation. A high voltage generated by the piezoelectric element may generate unwanted electric noises due to electrostatic induction, electromagnetic induction, leakage of current, radiation, etc. As a result, even when the circuit between the sensing electrodes is not closed, a voltage may be applied across the ignition discharge electrodes, and if the voltage is excessively large, even when the container is not filled with the material to be heated, the ignition operation may cause a spark discharge across the ignition discharge electrodes to ignite the exothermic system.
To solve this problem, the present inventors have proposed a container with a heating function, in which the voltage generated by the piezoelectric element was reduced to eliminate the escaping discharge electrodes, and, moreover, an electric circuit was provided to stabilize the electric pulses and reduce unwanted electric pulses so as to prevent ignition by improper operation. Furthermore, the inventors have proposed a bulb (see Japanese Patent Provisional Publication No. 4-150813) as a heat conversion apparatus which virtually converts electric energy into thermal energy and generates heat at high temperature for use in the above-mentioned container with a heating function. The bulb can be operated at a low voltage and has the following configuration: A thin metallic wire is sealed in a container containing oxygen, and a pair of separated electrodes are provided in the container. The surfaces of the electrodes are coated with an ignition agent which is an insulator or a resistor having a high resistance.
In this case, however, an extra electric circuit was required for stabilizing and reducing the electric pulses. The configuration of the circuit was complex, and the production process thereof was also complex and the cost was high since expensive electronic components were used. In addition, it was necessary to seal the metallic thin wire, etc. in the bulb used as the heat conversion apparatus, and the production process was complex, resulting in a higher cost.
In view of the above mentioned problems, one object of the present invention is to provide a container with a heating function, which requires no complicated electric circuit for stabilizing and reducing electric pulses and is free of any possibility of heat generation due to improper operation wherein a wrong ignition operation actuates the heat conversion apparatus to ignite the exothermic system.
Another object of the present invention is to provide a compact ignition apparatus having a simple construction, which requires no complicated electric circuit for stabilizing and reducing electric pulses and is free of any possibility of improper operation wherein an improper ignition operation actuates the heat conversion apparatus to ignite the exothermic system.
Another object of the present invention is to provide a heat conversion apparatus which is not actuated by a low voltage but requires a relatively high voltage and is applicable for said container with a heating function or ignition apparatus.